The present invention relates to methods and circuitry for measuring the temperature of an integrated circuit (IC).
In various contexts, the temperature of a given IC (otherwise referred to as a “chip”) may be measured by sensing the temperature at a temperature sensing pn junction within the IC. The IC may, e.g., be a personal computer (PC) processor chip, the temperature of which is controlled by operating a fan. The junction may be a diode or part of a bipolar transistor.
Some ICs are sensed externally or remotely, and thus have external terminals for coupling an internal temperature sense pn junction to a remote temperature sensing circuit. Other ICs are sensed internally, and thus have an on-chip temperature sensing circuit coupled directly to the IC's temperature sense pn junction.
There are a number of ways to determine the temperature of a pn junction, whether the junction is sensed internally or externally. One known method involves sequentially applying two different DC currents to the pn junction, and measuring the voltage across the pn junction, for the respective currents. The difference between the voltage values is then determined, which is used to determine the temperature of the sensed diode.
This known two current sequence method described above may provide inaccurate results, because it fails to adequately compensate for a parasitic resistance that develops across the sensed diode. Such a parasitic resistance may include the internal resistance of the sensed diode device as well as resistance associated with paths connecting the sensing circuit to the sensed diode.